1. Technical Field
The present invention relates to a printing apparatus and a method of controlling a printing apparatus.
2. Related Art
An ink jet printer allows an ink filled in a cavity of an ejection unit to be ejected and forms an image on a recording medium such as recording paper by allowing a piezoelectric element provided in the ejection unit of a head to be driven by a driving signal.
However, when the ink in the cavity is thickened, ejection abnormality occurs and the image quality of the image to be printed is degraded in some cases. Further, in a case where the ink in the cavity includes bubbles or paper dust is adhered to the vicinity of a nozzle of the ejection unit, ejection abnormality occurs and the image quality of the image to be printed is degraded in some cases. Accordingly, it is preferable to inspect an ejection state of the ink in the ejection unit for realizing high grade printing.
JP-A-2013-028183 discloses a technique of detecting residual vibration generated in the ejection unit which includes a piezoelectric element when the piezoelectric element is driven by the driving signal and inspecting whether the ejection state of the ink is normal by determining whether a cycle of the detected residual vibration is in a predetermined range.
On the other hand, the head of the ink jet printer is provided with a plurality ejection units. Among the plurality ejection units, an arrangement position of an ejection unit on the head is different from that of another ejection unit. Accordingly, physical properties of various constituent elements included in the ejection unit such as the piezoelectric element or the cavity, for example, compliance or the like of the cavity is different between one ejection unit and another ejection unit in some cases.
Accordingly, a cycle of the residual vibration generated in respective ejection units in a case where the plurality of ejection units are driven by the same driving signal is different between one ejection unit and another ejection unit in some cases. In other words, there is a case in which the range which can be obtained by the cycle of the residual vibration in a case where the ejection state of the ejection unit is normal is different between one ejection unit and another ejection unit.
Therefore, in a case of using a method in the related art of inspecting the ejection state of the ink in the ejection unit by determining whether the cycle of the residual vibration generated in the ejection unit is in a predetermined range, for example, when the predetermined range is decided such that the predetermined range does not coincide with the range which can be obtained by the cycle of the residual vibration generated in one ejection unit when the ejection state of the one ejection unit is normal, it is difficult to accurately determine the ejection state of the ink in another ejection unit. That is, in a case where the ejection state of the ink in the ejection unit is determined using a method in the related art, even if it is possible to accurately determine the ejection state on one ejection unit, but it is not possible to accurately determine the ejection state on another ejection unit, for example, the state may be erroneously determined as ejection abnormality even though the ejection state of another ejection unit is normal.